It's the biggest football match on the planet, and it's this Saturday.

El clásico pits two of the world's finest, most-successful clubs head-to-head and this weekend's fixture is laden with storylines to unpick and things to watch out for.

But first and foremost it's going to be about the three points on the line and the eleven players on the field as Real Madrid look to extend their lead atop La Liga.

Zinedine Zidane has some tough line-up decisions to make if he's to counter Barcelona's threat, but he has fewer injuries than his counterpart, Luis Enrique.

, but who will Zizou choose? Ed Malyon takes a look:

Keylor Navas

Unbeatable: Keylor Navas has been brilliant this season (Photo: Helios de la Rubia/Real Madrid via Getty)

The Costa Rican impressed everyone at World Cup 2014, and when he’s been given the opportunity at Real Madrid he has similarly dazzled.

So close to leaving the club on deadline day last summer, Navas was one of Madrid's best players as they won the Champions League under Zinedine Zidane.

He will need to be at his best to keep the Barca frontline at bay.

Dani Carvajal

Between a Roque and a hard place: Carvajal slips between two opponents (Photo: Victor Carretero)

The Spain full-back has fought off €30million worth of competition, so if he’s fully fit you’d always expect him to edge out Danilo with the Brazilian having experienced an up-and-down first season in La Liga last year.

Carvajal will have a hell of a task in keeping Neymar quiet down that side, as the Barca man has been in sensational form recently.

But he’s locked him down before and this is going to be one of the key battles that decides this game.

Sergio Ramos

Power Serg: Ramos will play through a long-term injury to be in el clásico (Photo: Antonio Villalba)

The Real Madrid skipper has struggled for form for the last 18 months and has increasingly been exposed by pace, with Mohamed Salah running riot against him in the Champions League knockout stages last season.

He needs to adapt his game to rediscover the form that made him one of the world's best at the position, though nobody can question his will to win.

Expect him to be really up for this game, but whether that will be enough to subdue Messi and co. is another question entirely.

Raphael Varane

Varane continues to improve (Photo: Getty Images)

The Frenchman has utterly frightening pace for a defender and that will be ideal when faced with a forward line like this.

Pepe's experience will be missed, especially when it comes to dealing with Luis Suarez's off-the-ball provocations.

Marcelo

Prone to leaving space in behind, Marcelo is a player often targeted by top-class opposition.

Roma and Paris Saint-Germain tried as much in the Champions League with some success last year, but despite an injury you’d have to say that the Brazilian remains the club's best option at left-back.

If Nacho were to start there instead then it would send a very negative message, and it would be a shock if Zidane benched Marcelo.

Isco

Real Madrid's Isco vies with Leganes's Mantovani and Machis

Isco steps in for Casemiro in a bold and attacking move by Zinedine Zidane.

The Spaniard has seized the opportunity to work his way back into the French manager's good books while Toni Kroos remains on the sidelines.

The combinations with Modric and Kovacic ought to plot Madrid's route into the final third.

Luka Modrić

'Rić pickings: Luka is vital for Madrid (Photo: AFP/Getty)

Real Madrid’s metronome and one of their most important players.

The Croat has been sensational over the last two seasons and still doesn't get the plaudits he deserves.

If they're to have a chance of winning this game, it will be because Modric has taken over the midfield.

Mateo Kovacic

Mateo Kovacic has virtually been a regular this season (Photo: AFP/Getty)

Learning from his idol, the young Croatian midfielder looked almost certain to return to Italy on loan after a first season in Spain that saw him get little gametime and make little impact.

Having take advantage of injuries in midfield, Kovacic's energy in the centre of the park has helped to keep Madrid's momentum going even when shorthanded.

Lucas Vazquez

Lucas Vazquez will replace Bale on the flank (Photo: Denis Doyle)

The young Spaniard broke into the team under Rafa Benitez after demonstrating work-rate and defensive awareness on the flank.

While Marco Asensio's rise has threatened Vazquez's playing time, the 25-year-old is a far more reliable performer and will play a key role in tracking Barcelona's full-backs at the Nou Camp.

Hidden beneath all that is that Vazquez is a danger in attack as well.

Cristiano Ronaldo

(Photo: PA Wire)

The Portuguese lit up this fixture in the spring with a sensational late winner and, if he can repeat that, he could virtually put the league title to bed before Christmas.

That would be quite a way to celebrate his monster new deal.

Karim Benzema

Happy times: Karim Benzema nets again (Photo: REUTERS/Sergio Perez)

Alvaro Morata has probably outplayed him but Benzema's long-standing chemistry with Ronaldo has saved his spot in the starting XI.

That may not last for too much longer but bagging a vital goal in the clásico is likely to buy him some time.

Missing out

James Rodriguez will likely have to settle for a place on the bench, as will Isco - but with the Spaniard having a chance of starting if Casemiro isn't fit. The defensive back-up is Nacho , while Danilo's inconsistent displays will likely see him benched.